TECHNIQUE:
           LIE  on the floor on your back
           place a rolled-up towel  (1 to 2 in. or 2.5 to 5cm, in 
          diameter)betweeen the small of your back and the floor
MUSCLES STRECTHED
     Most-strecthed muscles: Rectus abdominism external 
                                                        oblique, internal oblique
    Lesser-strecthed muscles: Quadratus lumborum, psoas, 
                                                           major, iliacus.
COMMENTARY:
Of all of the stretches in this , it stretch the lower trunk flexors, this is the best for people who have a swayed backs or have weak abdominal muscles, since arching the lower back is potentially dangerous for these people, Because the small back is supported in this exercise, undesired pressures on the spinal column are reduced, Nevertheless, the width of the back support is important, The larger the diameter of the object, the greater the undesirable pressure. Make sure that the upper back, shoulder blades, and  buttocks are resting comfortably on the floor, Also, squeezing the buttocks will reduce stress on the lower back.